The wifi toggle disconnects Apple’s iPhone or iPad from any wifi networks, but leaves the wireless radio available for use.
Photograph: Samuel Gibbs for the Guardian

The new, redesigned Control Centre in iOS 11, which appears to allow users to toggle various settings such as turning wifi and Bluetooth off, doesn’t actually turn them completely off.

Control Centre has a plethora of quick toggles, designed to allow users to quickly change a few key settings including activating the flashlight, turning off screen rotation and controlling the display’s brightness.

But two of the most used toggles, the ones for “turning off” wifi and Bluetooth, do not actually switch them off as a user might expect.

On iOS 11, pressing the wifi toggle immediately disconnects the iPhone or iPad from any wifi networks, but leaves the wireless radio available for use by location services, scanning for the names of nearby wifi access points. The Bluetooth toggle operates in a similar fashion. The reason, according to Apple’s documentation, is that both wireless systems are used for Apple’s file transfer and streaming systems AirDrop and AirPlay, using an Apple Pencil or Apple Watch, and for various other features including Handoff and Instant Hotspot.

Andrea Barisani (@AndreaBarisani)

On iOS 11 w/ Wi-Fi "disabled", auto-join for nearby networks off until "You walk or drive to a new location" or "It's 5 AM local time".

To actually turn off Bluetooth and wifi users will need to head into the Settings app and manually turn them off, which deactivates them until 5am the next morning, or use Airplane mode.

Apple says that by toggling wifi in Control Centre, the iPhone or iPad will not connect to any wifi networks until a user travels to a new location, they restart their device or the time ticks past 5am. Bluetooth, likewise, will not connect to any other devices until 5am the next morning or your restart your device.

But security researchers warn that having either wifi or Bluetooth active when not in use puts users at risk of attack, calling the change “stupid” and “not clear for the user”. Only recently researchers demonstrated that, due to a weakness in the implementation of Bluetooth in some smartphones and tablets, hackers could wirelessly hijack a device without the user having to accept a connection or download anything.

A similar thing happens in Android smartphones, which use wifi as part of their location services. Switching wifi off prevents it from connecting to wifi access points, but allows it to continue periodically scanning for access point names to help pinpoint its location.

In many smartphones, such as Samsung’s Galaxy S8 or Google’s Pixel, use of wifi and Bluetooth for location services can be altered in settings, and its use is generally explained within the wifi and bluetooth settings.

Leaving wifi and Bluetooth on all the time can also affect mobile phone signal and be a cause of battery drain, although more advanced systems are designed to mitigate serious impact on battery life by using them sparingly and in low-power modes. Together they help get a location lock much faster than the GPS chip alone and in doing so can reduce the power consumption of location services.